1. Field of the Invention
This invention relates to a navigation device that can display navigation data. The device find particular application as an in-car navigation system.
2. Description of the Prior Art
GPS based devices are well known and are widely employed as in-car navigation systems. Reference may be made to the Navigator series software from the present assignee, TomTom B.V. This is software that, when running on a PDA (such as a Compaq iPaq) connected to an external GPS receiver, enables a user to input to the PDA a start and destination address. The software then calculates the best route between the two end-points and displays instructions on how to navigate that route. By using the positional information derived from the GPS receiver, the software can determine at regular intervals the position of the PDA (typically mounted on the dashboard of a vehicle) and can display the current position of the vehicle on a map and display (and speak) appropriate navigation instructions (e.g. ‘turn left in 100 m’). Graphics depicting the actions to be accomplished (e.g. a left arrow indicating a left turn ahead) can be displayed in a status bar and also be superimposed over the applicable junction's/turnings etc in the roads shown in the map itself. Reference may also be made to devices that integrate a GPS receiver into a computing device programmed with a map database and that can generate navigation instructions on a display. The term ‘navigation device’ refers to a device that enables a user to navigate to a pre-defined destination. The device may have an internal system for receiving location data, such as a GPS receiver, or may merely be connectable to a receiver that can receive location data.
It is known to enable in-car navigation systems to allow the driver, whilst driving in a car along a route calculated by the navigation system, to initiate a route re-calculation. This is useful where the vehicle is faced with construction work or heavy congestion.
Reference may be made to U.S. Pat. No. 6,118,389 which discloses techniques for calculating a re-route. Initiating the re-route calculation requires activation of a specific detour switch, which may however be inconvenient to the user. Reference may also be made to U.S. Pat. No. 5,544,060, which enables a device to preview the calculated route by displaying in successive screens each different road and turning that the vehicle has to take; the user however has to manually sequence through each successive screen using a preview switch until he reaches the road that he wants to exclude from the route; he then selects a cancel switch; a new route is calculated which excludes the cancelled road.
The present invention aims to improve on the user interaction aspects of initiating a route recalculation.